This invention relates to a colorimetric indicator testing device or card for determining the presence of a specific substance in a liquid medium.
The widespread use of a wide variety of substances in an equally wide variety of environments has made repeated testing for the specific substances necessary in order to control, for example, antibiotic dosages or to determine whether fields which have been treated with various types of organic insecticides are safe for field workers to enter.
Conventional methods of testing entail the drawing or making of a sample of the substance to be tested. For instance, where paraquat is utilized in spraying vegetation, a sample of the vegetation which has been sprayed is taken to the laboratory and a liquid suspension of the paraquat is made which is then subjected to a series of conventional laboratory tests to determine whether the paraquat has been dissipated or whether the amount remaining is so small as to render it safe for workers to enter the paraquat-sprayed field. Naturally, the necessity for remote testing of the specimens of the substance entails consumption of time which delays the harvesting or other necessary treatment of crops.
Similarly, where patients are subjected to large doses of antibiotics, such as neomycin, gentamicin and the like, it is customary to draw blood and to take the blood samples to a hospital laboratory or other laboratories which then make the requisite test necessary to determine the amount of antibiotic present in the blood of the patient. Such remote testing, once again, delays immediate action upon the part of the hospital staff to curb or enlarge the antibiotic dosages as a result of the test indications.